Thermal emission from absorbing material is considered to be incoherent and unpolarized, and accordingly is regarded as spontaneous emission. The surface properties of the absorbing material have a profound impact on the emission's optical properties, and can be manipulated to produce a partially coherent and partially polarized radiation emission. Recently, it was shown that by etching a uniform grating on a SiC substrate, a highly directional peak of thermal emission was achieved. Furthermore, spectral resonance and nondirectional emission were observed at certain frequencies. In these instances, a connection between the emission and the surface properties was established by studying the excitation of surface phonon-polaritons (SPPs). The underlying microscopic origin of the SPP is the mechanical vibration of the atoms. A surface polariton (phonon or plasmon) has a longer wave vector than the light waves propagating along the surface with the same frequency. For this reason, they are called “nonradiative” surface polaritons. By coupling the surface polaritons with the propagating wave by means of an additional prism or grating, one can produce either increased resonant absorption or directional emission. Because SPPs or surface plasmon-polaritons are able to be excited only by TM-polarized propagating waves, the emission's characteristics have to be polarization-dependent. The TM polarization state has an electric-field component that is parallel to the grating vector (see inset in FIG. 1(a) for TE and TM definitions).